The secondary factor, which is responsible for meandering in an alluvial river, is
Permeable spurs are best suitable for rivers, which
Permeable spurs or groynes do permit restricted flow through them. Permeable groynes, simply obstruct the flow, reducing its velocity and causing silt deposition. They are, therefore, best suited for river carrying huge sediment lead in suspension.
Denehey’s spur is
Denehy’s groyne is a special type of groyne which is
Denehy’s T-shaped groyne is a special type of groyne developed in India for protection of bank. It comprises of ordinary groyne with an extra cross groyne at the head giving it T-shape.
Hockey shaped groyne is an attracting type of groyne.
Groynes are adopted for river bank protection works. When it is placed inclined downstream in the direction of flow in the river, it is designated as which one of the following?
A groyne pointing downstream has the property of attracting the flow towards it and is called an attracting groyne. In attracting groynes scours holes are developed nearer the bank, as compared to those in a repelling groyne. Since such attracting groynes bring the water current as well as scour holes nearer the bank and make it more susceptible to damage, they are not used generally. The groynes are therefore, generally aligned either perpendicular to the bank or pointing upstream (repelling groyne).
Under which one of the following categories is the river Ganga classified in the reach through UP and Bihar ?
Formation of successive bends of reverse order in a river may lead to the formation of a complete S curve called meander. Such a river is called meandering river.
When a river flows in two or more channels around alluvial islands, it is known as a braided river.
Deltaic river is a river which gets divided into branches before joining the sea, thus forming a Δ shaped delta.
Consider the following statements:
1. High water training is undertaken to protect against damage due to floods.
2. Low water training is undertaken to provide sufficient depth for navigation.
3. Mean water training is undertaken to provide efficient disposal of sediment load.
Which of these statements is/are correct?
1) High water training works ( training for discharge )
High water training works are constructed for the purpose of quick disposal of maximum flood and to protect adjoining land against damage due to floods. It aims to provide sufficient river cross-section for stage passage of maximum flood.
2) Low water training works (training for depth)
It is undertaken with the primary purpose of providing sufficient water depth for navigation during a low flow period. Generally, spurs are constructed to contract the width of the channel and hence to increase the depth.
3) Mean water training works ( training for sediments )
It is undertaken with the primary purpose of providing efficient disposal of sediment load and bedload thus preserving the channel in good shape. It is the most important training of the three types.
An attracting groyne is one which is
A Groyne painting downstream has the property of attracting the flow towards it and is called an attracting groyne. In attracting groynes scour holes are developed nearer to the bank, as compared to those in a repelling groyne.
A river training work is generally required when river is
Which of the following are the purpose of a groyne as a river training structure?
1. It contracts a river channel to improve its depth.
2. It protects the river bank.
3. It does not allow silt to deposit in the vicinity.
4. It trains the flow along a certain course.
Select the correct answer using the codes given below:
Groynes are embankment type structures, constructed transverse to the river flow, extending from the bank into the river. They are constructed to protect the bank from which they are extended,' by deflecting the current away from the bank. These are called repelling groynes. On the upstream side of a repelling groyne, a still water pocket is formed, where the suspended sediments carried by the river, gets deposited. For low water training or training for depth groynes can be used; Herein they contract the width of the channel to provide sufficient depth for navigation during low water periods.
In order to train the flow along a certain course guide banks are most commonly used. However groynes can also be used to deflect the flow or attract the flow.